1. Field of the Invention
This invention relates to photographic silver halide elements of the negative and direct positive types having improved sensitometric characteristics when developed in the presence of a heterocyclic-substituted or a thioaryl substituted tertiary phosphine.
2. Description of the Prior Art
Various prior art patents teach the use of phosphorus compounds in photographic emulsions. Cowden et al. U.S. Pat. No. 3,057,721 issued Oct. 9, 1962, teach photographic emulsions containing tanning and non-tanning developers and trialkyl phosphite and a monocyclic triaryl phosphite of the benzene series.
Dunn, U.S. Pat. No. 3,297,446 issued Jan. 10, 1967, claims a photographic silver halide emulsion sensitized with a noble metal sensitizer and a labile selenium sensitizer, said emulsion containing an antifoggant amount of an organic tertiary phosphine. No heterocyclic or thioaryl phosphines are disclosed.
Thurston, U.S. Pat. No. 3,338,712 issued Aug. 29, 1967, claims a sulfur sensitized emulsion containing from 5 to 500 mg. of trialkoxy and triaryloxy phosphite.
Dunn, U.S. Pat. No. 3,442,653 issued May 6, 1969, teaches the use of reducing agents, triphenyl phosphine being one, to convert selenium in situ to the labile state for sensitizing photographic silver halide emulsions.
Bloom, U.S. Pat. No. 3,578,449 issued May 11, 1971 teaches the incorporation of organic phosphine in photographic processing compositions for use in silver diffusion techniques. No heterocyclic or thioaryl substituted tertiary phosphine is shown.
Bloom, U.S. Pat. No. 3,594,169 issued July 20. 1971, discloses the use of water-soluble tertiary aliphatic phosphines as silver halide solvents in photographic processing compositions having a pH in the range of 4 to 9 for carrying out diffusion transfer processes.
Buckler et al., U.S. Pat. No. 3,640,713 issued Feb. 8, 1972, discloses hydroxyl and/or amine substituted tertiary organic phosphines for use in photographic processing compositions for carrying out diffusion transfer photographic techniques.
Bloom, U.S. Pat. No. 3,644,530 issued Feb. 22, 1972, discloses the preparation of (2,5-dihydroxyphenyl) diphenyl phosphines and discloses that they may be used as sequestering agents, as antifoggants, and as surfacants.
Pollet et al., U.S. Pat. No. 3,681,078 issued Aug. 1, 1972, discloses as antifoggants for silver halide emulsions, compounds represented by the formula R--Se--Q wherein R stands for alkyl, aralkyl, or aryl which may be substituted by halogen, sulfo, carboxyl or nitro or form part of a heterocyclic ring, and Q stands for halogen, cyano, or PR.sub.3 .sup.+X.sup.- wherein each R independently stands for alkyl, aralkyl or aryl and X.sup.- stands for an anion but does not exist when R itself contains an anionic group.
Florens et al., U.S. Pat. No. 3,717,466 issued Feb. 20, 1973 claims direct positive silver halide elements which have been uniformly fogged by radiation or chemically with a reducing agent and containing as a sensitizer a selenium compound corresponding to the following formula: R-- Se-- Q wherein R stands for an alkyl group, an aralkyl group, an alkaryl group, an aryl group or a heterocycle. Q stands for --Se --R.sup.1 or -- S -- R.sup.1 stands for alkyl, aryl, aralkyl, alkaryl, heterocyclic, halogen, --CN or PR.sub.3 .sup.+X.sup.- where each R independently stands for alkyl, aralkyl or aryl and X.sup.- stands for an anionic group.
The prior art does not, however, teach the use of a heterocyclic or thioaryl phosphine in or for the development of a negative or direct positive type silver halide emulsion.